Cardiac dominance is based on ?

Ans. is 'd' i.e., 10thRibsThere are 12 pairs of ribs. All aiculate posteriorly with thoracic veebrae. The ribs are divided into two types.True ribs or veebrosternal ribs :- These are lst to Th ribs which aiculate directly with sternum through costal cailages.False ribs :- These are 8" to 12th ribs and do not aiculate directly with sternum. False ribs can be divided into:Veebrochondral ribs :- 8th,9th and 10th ribs whose costal cailages aiculate with each other and with 7th costal cailage forming costal margin,Floating ribs (veebral ribs) :- 11 ''' and 12th ribs have free anterior ends.The ribs can also be divided into ?Typical ribs :- 3rd to 9th ribs are typical ribs because they bear common features and individual indentification is not possible.Atypical ribs (peculiar ribs) :- 1", 2nd, Oth, 11`h, and 12th ribs are atypical and each of them can be identified by special distinguished features.